Dementias that present with and without posterior cortical features: an important clinical distinction.

There are distinct qualitative differences between the dementias that present with and without posterior cortical features. These can be utilized in dementia assessment. This paper reviews the validity and potential utility of a dichotomy based on generalized cortical (Type 1) versus isolated frontal system pathology (Type 2). These syndromes are associated with distinct differentials and problem behaviors. They may also result in different caregiving burdens or treatment responses. Alzheimer's disease (AD) is by far the most common cause of the Type 1 syndrome. Type 2 presentations select for potentially reversible non-AD conditions. Common cognitive screening instruments are insensitive to Type 2 cases. However, the Type 1/Type 2 distinction can be made reliably using qualitative clinical rating scales. We will review these instruments and discuss their application in clinical settings.